You mean this one ?
Capricorn tube- https://www.amazon.com/dp/B086YPDHMF/ref=cm_sw_r_cp_apa_fabc_v9m0FbETXP8V8?psc=1
Nozzle
https://www.amazon.com/dp/B07L1C7J77/ref=cm_sw_r_cp_apa_fabc_Rcn0FbDDR1A9F
Lots of good thoughts in here. One thing that's nice about the Mini is that it's very full-featured out of the box. Some printers have a laundry list of must-have accessories, but the Mini is great from the start. Not that you can't accessorize:
Nozzles
Maybe the most fun-for-the-dollar thing to get would be a brass nozzle kit a-la https://smile.amazon.com/E3D-Extra-Nozzle-1-75mm-V6-NOZZLE-PACK-175/dp/B013VBTM80?sa-no-redirect=1. The standard nozzle is 0.4mm which is great for most things. But a smaller opening means you can print much greater detail, and a bigger opening means you can print bigger parts faster, and often stronger.
I second (or third) the Nozzle X as a good accessory, but maybe not a right-away accessory. https://smile.amazon.com/Genuine-E3D-Nozzle-V6-1-75mm-V6-NOZZLE-4TC-175-400/dp/B07L1C7J77/ref=pd_lpo_2?pd_rd_i=B07L1C7J77&psc=1. It's necessary if you're going to be printing abrasive materials including glow-in-the-dark filament, glitter filament, wood filament, and anything with carbon fiber in it. Carbon filaments can be a pain, but offer a lot for the trouble. In other words, you don't NEED a hardened nozzle until you're printing materials that already take some getting used to. And hardened steel doesn't conduct heat as well as brass, so it's best to get used to a standard brass nozzle first.
Build Sheets
The mini can be had with a smooth or textured build surface. I love both for different things, so whichever your husband doesn't have, the other might be a good accessory. https://www.prusa3d.com/product/mini-spring-steel-sheet-with-smooth-double-sided-pei/ and https://www.prusa3d.com/product/mini-double-sided-textured-pei-powder-coated-spring-steel-sheet/
Filament
So many options here. The plastic options are PLA, PETG, ASA, ABS, Nylon and a bunch of more exotic options. PLA is easiest and probably safest. PETG is only slightly more difficult and offers some advantages and disadvantages. I'd start with those two, and probably both. Brands include hatchbox, protopasta, printedsolid jessie, oh and Prusament!, and others, but those are top-tier that I've used. PLA and PETG should run you $20-30/kg for good stuff. Cheaper stuff can be worth it, but best get used to premium quality so you get a sense of which problems are you vs the cheap filament. Any of those options carbon-fiber filled would be fun and worth trying, but also difficult so maybe not if its his first printer.
Cura Start Code:
; AnyCubic Kobra and Kobra Max Custom Start G-code
M140 S{material_bed_temperature_layer_0}; Heat bed
M104 S{material_print_temperature_layer_0}; Heat extruder
G92 E0 ; Reset Extruder
G28 ; Home all axes
M190 S{material_bed_temperature_layer_0}; Wait for bed to get up to temperature
M109 S{material_print_temperature_layer_0}; Wait for extruder to get up to temperature
G1 Z2.0 F3000 ; Move Z Axis up little to prevent scratching of Heat Bed
G1 X0.1 Y20 Z0.3 F5000.0 ; Move to start position
G1 X0.1 Y200.0 Z0.3 F1500.0 E15 ; Draw the first line
G1 X0.4 Y200.0 Z0.3 F5000.0 ; Move to side a little
G1 X0.4 Y20 Z0.3 F1500.0 E30 ; Draw the second line
G92 E0 ; Reset Extruder
G1 Z2.0 F3000 ; Move Z Axis up little to prevent scratching of Heat Bed
G1 X5 Y20 Z0.3 F5000.0 ; Move over to prevent blob squish
;End of Custom Start Code
Printer Nozzles:
Hotend explained and how to properly change the nozzle on a 3D printer
Is my 3d Printer Belt too tight?
General Trouble Shooting Steps:
Where do I find things to print?
Where do I start if I want to make my own object to print